244 
J. STUAET THOMSON. 
lionr’s time a layer of mucus had become deposited ou the 
sides of the groove. 
Ou adding chloroform to the water in which the rockling 
is living, the movement of the vibratile fin ceases, although 
the animal freely moves its pectoral fin. Similarly, the 
addition of cocaine to the water containing’ a small rocklinsf 
O O 
(2-3 in. in length) has the effect of stopping the movement 
of the rays for intervals varying from forty seconds to three 
minutes. 
The action of the vibrating processes apparently maintains 
a clear area of skin on either side of the groove. My experi- 
ments, which consisted in letting down granules of carmine 
by means of a pipette, show that while tliese grains readily 
adhere to most parts (probably from the secretion of mucus), 
yet there remains an area on either side which keeps clear of 
carmine particles. The absence of carmine particles soon 
delineates very distinctly the area of vibration from the pig- 
mented skin of the genei’al surface of the bodv. A similar 
result evidently occurs when the fish is living in its natural 
habitat, as I have repeatedly noted that when I’ockliugs are 
brought in from the shore they have a coating of sand on 
the general surface of the skin, with the exception of the 
area immediately surrounding the vibratile fin. 
AVhen the vibratile fin ceases movement, the large anterior 
process is folded backwards over the smaller processes, and 
these in their turn over those situated more posteriorly. 
On lightly touching the sides of the groove, the processes 
fold themselves down on the opposite side of the groove to 
that which has been touched. 
In the light of my subsequent remarks, it is interesting to 
notice that contact on the barbules and pelvic fins results iu 
renewed movement of the vibrating rays when this has been 
stopped, but that the same result does not take place on 
contact with the pectoral fins. We will later notice that the 
barbules and pelvic fins have the same general mode of 
innervation as the area under discussion. 
Bogoljubsky coated the rays from the dorsal surface with 
